1. Field of the Invention
The present invention relates generally to a suspension assembly for a vehicle and more specifically to an improved suspension assembly for a wheeled vehicle such as an agricultural boom sprayer in which a stable platform is particularly desirable.
2. Description of the Prior Art
Various suspension systems for wheeled or other land vehicles currently exist in the art. A typical suspension system includes a pair of shock absorbers and/or other spring means positioned between the vehicle chassis and a generally horizontally disposed axle having a wheel or other terrain engaging means at each end. There are various types of spring means which are utilized in these suspension systems. Commonly used spring means includes heavy coiled springs, air cylinder type springs or air bags which are filled with air or other gas and which function to cushion the vehicle as it traverses the terrain.
It is also common when air bags or other air springs are utilized to employ a metering valve in conjunction with the air springs. Such metering valves detect the position of the axle relative to the vehicle chassis and either inject air into, or release air from, the air bag or air spring, depending upon the specific relative position between the axle and the chassis. Although the above described suspension systems are generally satisfactory for most vehicular applications, unique problems arise for vehicles such as boom sprayers and other vehicles which typically move across irregular terrain surfaces and which requires a stable spray boom supporting platform.
For example, a boom sprayer can embody spray boom sections which extend outwardly from opposite sides of the vehicle as far as fifty feet or more. Because of this structure any tilting movement or other instability of the boom supporting platform is magnified many times at the tip of the boom. Thus, a tilting movement of the supporting platform of a couple of inches can result in corresponding movement at the boom tip of several feet or more. This problem is further compounded by the fact that it is extremely important for a vehicle such as an agricultural type boom sprayer to maintain the boom and the boom tip as stable as possible. Such stability is necessary to prevent damage to the boom and sprayer itself, to allow for more accurate and economical chemical application and to minimize damage to the crops and the environment. These latter factors have become increasingly critical in view of the extremely high environmental standards which must now be adhered to as well as the high cost and the extreme potency of the chemicals or other sprays being delivered.
Some suspension systems have been designed with specific application for boom sprayers. One such system includes a separate parallelogram type linkage for each vehicle wheel with one end connected with the wheel, a second end connected with the vehicle chassis on the wheel side of the center and the immediate portion being cushioned by an airbag or other spring means. Although this structure provides greater stability than ordinary suspensions, additional stability is still needed and desired. Accordingly, there is a need for a suspension system for a boom type sprayer or similar vehicle which is capable of providing a stable boom supporting platform while such vehicle traverses irregular and bumpy terrain.